Shameless promotion for the Pyramid web framework and friends, disguised as thoughtful posts about web development.

Pyramid has a powerful mechanism for configuring which view code
should be called for each web request. Basically, it allows you to
use any information from the request to select the view that will be
executed. This is mostly done in the form of predicate expressions
that are part of the view configuration. This post is an overview of
the available predicates and their use.